Dynamo-electric machine ventilation



March 3, 1936. R. B. wxLLiAMsoN DYNAMO-ELECTRIIC MACHINE VENTILATION 2 'SheeJcs-SheecI 1 Filed OG'. 26, 1933 msi 42160/25527 fr Mardi 3, 1936. R, B. WILLIAMSON DYNAMO-ELECTRIC MACHINE VENTILATION Filed Oct. 26, 1933 2 Sheets-Sheet 2 Patented Mar. 3, 1936 UNITD STATES PATENT OFFICE DYNAMO-ELECTRIC MACHINE VENTILATION Application October 26, 1933, Serial No. 695,295

14 Claims.

This invention relates in general to dynamoelectric machines and has more particular relation to the cooling of the rotor elements of high speed dynamo-electric machines, as for instance, the rotating field element of an alternating current generator .designed to be driven by a steam turbine.

In the design of turbo-generators, desired high speed operation of the machine makes it desirable to hold the diameter of the rotating element to a suitably small dimension, and with the rotor of relatively small diameter so as to insure safety in withstanding stresses due to centrifugal force, large capacity of a machine of this character is attained by suitably increasing the aXi-al length of the machine. With this situation of relatively small diameter and extended length of rotor, the problem of properly maintaining the rotor core and Winding at a suitably low operating temperature becomes a very consider-able one. And where the rotating field of a turbogenerator is of the well known solid forged construction, wherein the field core is formed as a single forging, the ventilation problem is especially serious. Ordinary prior art practice in Ventilating cores of high speed machines of relatively great capacity has included the provision of longitudinal apertures through the core, one or more fans being provided for forcing ventilating air through these longitudinal passages, and in some cases the construction being modified to include radial yducts communicating with the longitudinal ducts and permitting air to be discharged outwardly through the radial ducts into the air gap. However, with a rotor of considerable lengthit is difficult to provide for longitudinal passages of suflicient cross-sectional area to insure the necessary volume of ventilating air throughout the core body without unduly weakening the rotor, or, if suitable provision for strength is made, without unduly increasing the .diameter of the core.

In accordance with the present invention, provisions may be m-ade for insuring increased ventilating effects in a rotary core element without unduly weakening the same or increasing the diameter of the core beyond the minimum safe diameter, and through practice of the invention, the desired Ventilating effects may be present at the hotter portions of the core body, more particularly adjacent the inner part of the Windingcontaining slots, with the resultant effect that heat is readily removed from interior portions of the core, and the winding is maintained at a satisfactory low temperature which insures increased efliciency and permits increased loading of the machine. And advantages of the present invention may be realized through the provision of Ventil-ating passages at spaced points and extending through interior portions of the core, with the inlet for cooling air through these passages opening through the periphery of the core, and the discharge from these passages preferably likewise through the periphery of the core.

It is an object of the present invention to provide an improved design and construction of a dynamo-electric machine embodying an improved arrangement for Ventilating interior portions of the core.

It is a further object of the present invention to provide an improved design land construction of a dynamo-electric machine wherein the rotary core element, particularly one of the solid, usually forged, type, is provided with Ventilating passages arranged to admit cooling air or the like from the peripheral portions of the core during rotation thereof and to discharge such ventilating air likewise through the peripheral portions of the core removed from the inlets to such passages, after the air has been passed in contact with interior heated portions of the core.

It is a further object of the invention to provide an improved design and construction of a dynamo-electric machine of the character set forth wherein the inlet portions of the ventilating passages in the core are of special formation to facilitate the feeding of cooling air or the like through the periphery of the core to the interior thereof.

These and other objects and advantages are attained by the present invention, various novel features of which will be apparent from the accompanying description and drawings, disclosing an embodiment of the invention, and will be more particularly pointed out in the claims.

In the accompanying drawings:

Fig. 1 is a fragmental vertical section of a dynamo-electric machine embodying features of the present invention;

Fig. 2 is a fragmental vertical section through the stator of the machine in the plane of the line II-II of Fig. 1;

Figs. 3 and 4 are enlarged plan views of portions of the rotatable element of the machine of Fig. 1;

Fig. 5 is an enlarged fragmental vertical section in the plane of the line V-V of Fig. 4;

Fig. 6 is an enlarged fragmental vertical section in the plane of the line VI--VI of Fig. 4;

Figs. 7 and 8 are views similar to Figs. 4 and 5, respectively, showing a modied embodiment of the invention, the plane of Fig. 8 being that of the line VIII-VIII of Fig. 7;

Figs. 9 and 10 are Views similar to Figs. 4 and 5, respectively, showing a further modiiied embodiment of the invention, the plane of Fig. 10 being that of the line X-X'of Fig. 9.

In accordance with the disclosure of the drawings, wherein the invention is shown applied to a turbo-alternator designed for high speed operation and whose rotating iield element includes a core of solid, usually forged, construction wherein the core and shaft are formed as a single forged element, the stator element of the machine includes a housing 9, of conventional design, having end bells or shields I0 at each end thereof. A core I2 of the laminated type is made up of suitably spaced groups of laminae, the spaces between the several groups providing radial ventilating ducts, indicated at I3; and the core laminae are slotted at their inner periphery for the reception of an armature winding I4 which is suitably held in position in the slots.

Normal ventilation of the stator core is secured through a series of spaced longitudinal ventilating passages or ducts I6 opening from both ends of the machine and being open at their radially inner side, the radial walls of these passages constituting a frame or support upon which the stator core laminae are mounted and suitably held in position as by means of end clamping heads I 1. During operation of the machine, Ventilating air currents are drawn in through the end bells in conventional manner, as here shown being drawn from the lower side of the end bells, this air passing over the extending end turns of the stator winding I4 and 'into the Ventilating ducts or channels I6, thence radially inward into the radial spaces or ducts v I 3 between the laminae, the air inits passage through the core dissipating heat from the latter and portions of the winding which pass through the Ventilating spaces I3. A portionv of the air passes circurnferentially to either side in the radial spaces I3 and radially outward therefrom through passages I8 formed by the side walls of adjacent ducts I6, to a chamber in the frame of the machine and thence eX- ternally of the machine. Another portion of the Ventilating air entering through the ducts I6 may pass inwardly to the air gap and may be utilized in Ventilating the rotor, as vwill be described hereinafter.

The rotary element of the machine may be considered as including a core of the solid, usually forged, type, whether it be one wherein the core body and shaft are forged from` a single billet, or one wherein the core body, in one or more sections, and stub shafts are formed separately and the stub shafts are later secured to the end of the core body. Radial slots 23 are disposed in conventional manner at the periphery of the core, coils 24 of a conventional form of eld winding being held in place in these slots by wedges 25, the wedges being held in position by dovetail portions thereon cooperating with suitably formed portions of the side Walls of the teeth 26 provided between the slots 23. The outer faces of the wedges 25, especially at the side Aedges thereof, are preferably disposed a substantial distance from the outer periphery of the rotor core.

In the teeth 26 between adjacent slots 23 are formed, as by boring, substantially radial apertures 21 extending from the periphery inwardly well along toward the bottom or inner end of the slots, while maintaining any desired suitable thickness of metal between the apertures and the slots. Intersecting each of these substantially radial apertures 21 is an aperture 28 bored from the periphery of the core at a substantial angle to the aperture 21, the plane of the axis of the two apertures 21,28 being generally longitudinal of the aXis of the core and substantially parallel to the winding disposed in the core slots. The pairs of intersecting Ventilating apertures 21, 28 may well be arranged in longitudinally alined series, particularly for convenience in machining; and the point at which theaperture 23 intersects the periphery of the core can well be substantially intermediate adjacent apertures 21 of the same longitudinal series; and an eifective arrangement for normal turbo-generator speeds may well be one wherein the aperture 2S intersects the aperture 21 at an angle of approximately 35 degrees.

The apertures 21 may be termed inlet apertures, the apertures 28 being likewise termed discharge apertures. The radially outer end of the apertures 21 is formed to facilitate the entrance of air into the aperture during rotation of the rotor, this effect being produced by providing a substantial directional component in the direction of rotation of the rotor or a tangent to the periphery of the rotor, with the entrance to the passage or aperture at the leading side or edge thereof, considered with respect to the direction of rotation. While this desired formation of the radially outer end of the inlet apertures 21 may be formed by merely cutting away the metal at the periphery of the core in a suitable fashion, it is preferable to provide separately formed and suitably shaped nozzle or inlet portions at the outer end of these apertures 21.

As indicated, the outer end of the inlet apertures 21 isl provided with a counter-bored portion 29. In this counter-bore, there is placed an apertured plug or inlet member or nozzle 30 suitably secured, as by a threaded connection between the parts, in position within the counter-bore. A slot may be provided in the outer face of the plug 30 for the reception of a tool to facilitate insertion of the plug to desired position in the counter-bore. The inlet plug 30 is provided with an aperture or recess 3l providing .a passage of cross-sectional area preferably at least equal to that of the aperture 21 and extending from the inner end of the plug and opening through its side wall, with the outer end of the plug substantially closed. The inlet plug or nozzle may be secured against movement from position in the counter-bore 29, as by set screws cooperating with the material ofthe plug and core or by welding or otherwise, with the opening through the side wall of the plug facing in the direction of the rotation of the core.

'Ihe material of the core at the periphery thereof is cut away up to the adjacent winding slot 23, as indicated at 32, to provide a passageway or recess with an outwardly inclined inner wall 34 and communicating with the periphery of the core and the space radially outside the slot wedge 25.

Through the arrangement described, an inlet nozzle portion is provided for the inlet apertures or passages 21 which opens in the direction of rotation of the rotor and isy free to receive ventilating air during such rotation, the walls, particularly the outer wall of the passage 3| through the inlet nozzle, acting as a scoop or fan element which draws in a current of air during normal operation of the rotor, with suicient pressure built up to force the air inwardly a through vthe passage 21 and again outwardly through the inclined discharge aperture 28, the air being discharged from aperture 28 at a substantial positive pressure, thus insuring continuous passage of a relatively large volume of air through the Ventilating ducts formed by the communicating apertures 21, 28. This air is discharged from the .apertures 28, eventually passing outwardly .through the air gap and the radial Ventilating spaces I3 between groups of stator laminae and through the passages i8 to the discharge for the stator Ventilating system.

As indicated at 36, the trailing or both leading and trailing, edges of the teeth 26 adjacent the air gap may be rounded off, thus hindering or reducing eddying of air in the spaces or pockets outside of the slot wedges. The periphery of the rotor core may be provided with a multiplicity of circumferential grooves 38 providing spaced annular teeth which assist in cooling peripheral portions of the core, particularly through increasing the heat dissipating surface. However, it is preferable to leave the portion of the periphery immediately adjacent the nozzles 30 ungrooved, thus providing additional material to which nozzles or plugs are secured.

The pressure and volume of air passed through the Ventilating ducts formed by the communieating apertures 21, 28 may be increased to a substantial extent by forming the discharge end of the apertures 28 with a directional component opposite to the direction of rotation of the rotor. This discharge formation may be produced by providing the outer end of the aperture 28 with a counter-bore and a plug or nozzle 30e, indicated in Fig. 4, generally similar to the plug 30 lat the inlet end of the aperture 21 and secured in position in alike fashion, with the opening through the side wall of the nozzle in a direction opposite to the direction of rotation of the rotor and with the adjacent portion of the core periphery recessed toward the leading side of the adjacent winding slot, as indicated at 32l in Fig. 4.

In the modication shown in Figs. '7 and 8, the arrangement of Ventilating ducts in the rotor core is somewhat different from that described in Figs. 1 to 6. Teeth 26 are bored inwardly to their full depth and slightly beyond, adjacent teeth being provided with an inlet aperture 21a and a discharge aperture 28a, the outer end of the inlet aperture being counter-bored and provided with a plug or nozzle 30 and the periphery of the core at the leading side of the nozzle being recessed at 32, all as more particularly described in connection with Figs. 1 to 6. The inner end of the apertures 21a and 28a are connected by a passage formed by recessing, as by boring, the inner end wall of the winding slot 23 at a point in line with apertures 21a and 28a, as indicated at 4|, and to .a `depth corresponding to the inner end of these apertures, and by further machining out or recessing the side walls of the recess 4| as indicated at 42, 43 so asl to provide communication between recess 4| and apertures 21e, 28a, respectively. This provides a continuous Ventilating duct from the nozzle 30 through inlet aperture 21a, recesses 42, 4| and 43, ,and discharge aperture 28a, permitting the passage of the stream of Ventilating air therethrough. It is preferable to dispose strips of heat conductive metal, indicated at 45, at the inner end of the slots 23, this serving to protect the insulation on the winding and to assist in dissipating heat therefrom to the core.

Instead of having the discharge aperture 28a in the same radial plane as the inlet aperture 21a, these two apertures may be offset and the recesses 4|e, 4|b in the bottom of the winding slot opposite the apertures 21a, 28e, respectively, connected by a longitudinal groove 46 formed in the inner end wall of the slot 23, as more particularly indicated in Fig. 7, thus providing a path from the inlet aperture 21e, through the recesses 42, 41e, thence in a longitudinal direction through the groove 46 beneath the winding 24, and thence through recesses 4| and 43 and discharge aperture 28e. The above general arrangement provides intimate contact between the cooling air and more extended portions of the core and winding at the inner ends of the winding slots.

As shown in Figs. 9 and l0, the inlet and discharge apertures 21e and 28e, instead of being located in adjacent teeth, may be located in teeth separated by two or even more winding slots, communication between the inlet aperture 2`|a and the discharge aperture 28a being provided through a passageway formed through the material of the core beneath they winding in the two slots 23 intermediate the inlet and discharge passages 21a, 28a. This communicating passage includes a recess 48 provided at the bottom of the slot 23 adjacent the inlet passage 21a and a recess 49 provided at the bottom of the slot 23 adjacent the discharge passage 28a, these two recesses 48 and 49 communicating with each other at a point beneath the tooth 26 intermediate the latter twoslots 23, and recess 48 communicating with the inner end of inlet aperture 2'|EL and recess 48 communicating with the inner end of discharge aperture 28a. This arrangement provides a through Ventilating passage from the inlet nozzle 39, through the inlet aperture 21e, recesses 48 and 49, to the discharge aperture 28a.

In order to provide a more indirect path for the Ventilating air, insuring the passage thereof for a distance longitudinally of the core beneath the winding in the slots, a modified arrangement, as indicated at the lower right in Fig. 9, may be used. In accordance with this latter arrangement, a recess is provided at the bottom of the winding slot adjacent the inlet aperture 21a, this recess being in line and communicating with the latter; and a somewhat similar recess 52 is formed in the winding slot adjacent the discharge aperture 28a, this recess being in line and communicating with the latter. At a point removed from the inlet and outlet apertures 21a, 28e, recesses 53, 54 are provided at the bottom of the two winding slots which are between the inlet and outlet apertures, these two recesses communicating with each other. The bottom wall of each of these winding slots is provided with a groove of reduced width, one groove 55 extending between the recess 5| and the recess 53 and the other groove 51 extending between recesses 52 and 54. The upper side of the grooves 58 and 51 is preferably closed by the heat conductive strip 45. With this arrangement, there is a through passage for Ventilating air through inlet aperture 21e, recess 5|, groove 55, recesses 53 and 54, groove 51, and recess 52, to and through discharge aperture 28a, a considerable portion of the path being so= disposed as to bring the Ventilating in contact with the hottest portion of the core and windings.

Through the provision of a Ventilating arrangement embodying features of the present invention, it is possible to force a large Volume of Ventilating air through interior portions of the rotor core where the greatest heat is produced and has heretofore been most diilicult to dissipate; and though this provision the losses are so reduced as to substantially increase the eiiiciency and capacity of the machine, especially in a machine of relatively great axial length. And the desired results are attainable while holding the diameter of the rotor to a minimum value.

It'should be understood that the invention claimed is not limited to details of construction shown and described, for obvious modifications within the scope of the appended claims may be apparent to persons skilled in the art.

It is claimed and desired to secure by Letters Patent:

,1. A rotary core element for a dynamo-electric machine comprising a solid core body of magnetic material provided with through Ventilating ducts, each of said'ventilating ducts having an inlet and discharge portion and communication therebetween, and the open ends of said inlet and discharge portions being through the periphery of said body.

2. A rotary core element for a dynamo-electric machine provided with peripheral slots for the reception of a Winding, and Ventilating ducts having portions formed in the teeth between adjacent slots, the inlet and discharge portions of said ducts being spaced longitudinally of the axis of ro-tation of said core and having their inlet and discharge openings through the periphery of said core.

3. A rotary core element for a dynamo-electric machine provided with peripheral slots for the reception of a winding, and Ventilating ducts having portions formed in the teeth between adjacent slots and having their inlet and discharge openings through said teeth at the periphery of said core, peripheral portions of certain teeth being recessed at a side edge thereof to assist in providing a substantial directional component for certain of said openings through the periphery in the direction of a tangent ,to the periphery.

4. A rotary core element for a dynamo-electric machine provided with peripheral slots for the reception of a winding, and Ventilating ducts having portions formed in the teeth between adjacent slots and having their inlet and discharge openings through the periphery of said core, said inlet openings being through said teeth and having a substantial directional component in the direction of a tangent to the periphery of said core, and portions of the side edges of certain of said teeth at the leading side of said inlet openings being recessed to facilitate admission of air to said inlet openings.

5. A rotary element for a dynamo-electric machine provided with peripheral slots, a winding in said slots, and Ventilating ducts having portions formed in the teeth between adjacent slots and having their inlet and discharge openings through the periphery of said core, said inlet openings being through said teeth, wedges secured in the outer portions of said slots to retain said Winding therein, outer face portions of said wedges being spaced from the periphery of said core, and said teeth being recessed at their side edges to provide communication between the spaces radially outside of said wedges and the leading side of said inlet apertures to facilitate admission of air to said inlet apertures.

6. A rotary core element for a dynamo-electric machine provided with through Ventilating ducts each having its inlet and discharge openings for Ventilating fluid through the periphery of said core, a nozzle element separate from and secured in position at and having a through aperture forming the inlet end of said duct, the inlet end of the aperture in said nozzle element having a. substantial directional component in the direction of a tangent to said core. .l

'7. A rotary element of the solid type for a dynamo-electric machine provided with peripheral winding-receiving slots,v windings therein, and through Ventilating ducts having their inlet and discharge openings through the periphery of tooth portions of the core and the inlet openings extending in a direction having a substantial component in the direction of rotation of said core, said ducts including a portion disposed radially beneath a portion of the winding in the slots.

8. A rotary field element of the solid type for a turbo-generator, comprising a core provided with longitudinally extending peripheral slots. windings within said slots, and Ventilating ducts formed within said core adjacent the windingcontaining slots therein, said ducts each including inlet and discharge passages opening into the periphery of said core at spaced points, and communication between said passages, certain of said inlet passages extending through tooth portions between adjacent slots, an apertured nozzle element mounted in position at and its aperture constituting the outer end of each of said latter inlet passages, the inlet to said nozzle opening in the normal direction of rotation of said core, and the material of the tooth portion at the periphery thereof being recessed at its leading side to constitute a communication between the inlet to said nozzle and the outer portion of the adjacent winding slot.

9. A rotary core element of the solid type for a dynamo-electric machine, said core element being provided with through Ventilating ducts therein each disposed with its inlet and outlet in spaced relation longitudinally of the core and opening through the periphery of the core.

10.V A rotary core element of the solid type for a dynamo-electric machine, said core element being provided with through Ventilating ducts therein each disposed with its inlet and outlet in spaced relation and in substantial alinement longitudinally of the core and opening through the periphery of the core.

11. A rotary core element for a dynamo-electric machine provided with longitudinally 'extending peripheral winding-receiving slots forming normal tooth portions between adjacent slots and through Ventilating ducts each extending to in-v terior portions of the core, certain of said ducts each having its inlet and outlet openings through the-periphery of the core within the same tooth portion.

12. A core element of the solid type for a dynamo-electric machine provided with through Ventilating ducts, said ducts each extending to an interior portion of said core and having its inlet and outlet openings through the periphery of the core at points spaced apart longitudinally of the axis of rotation of said core.

13. A rotary core element of the solid core type for a dynamo-electric machine provided with longitudinally extending peripheral windingreceiving slots forming normal tooth portions therebetween and through Ventilating ducts each extending to interior portions of the core, each of said ducts having its inlet and outlet openings through the periphery of said core and having a uid inlet portion extending through one of said tooth portions and a fluid discharge portion extending through one of said tooth portions and an intermediate portion connecting said inlet and discharge portions and disposed radially within and in close proximity to the radially inner end of the winding-receiving portion of one of said slots immediately adjacent said tooth portion or portions.

14. A rotary element of the solid type for a dynamo-electric machine provided with peripheral slots forming tooth portions between adjacent slots, windings within said slots, and Ventilating ducts within said core adjacent the winding slots therein, each of said ducts including an inlet and discharge passage opening to the periphery of said core at spaced points and communication between said ducts, the inlet passages of said ducts passing through said tooth portions to the periphery thereof, and a separately formed apertured inlet element mounted in position at and at least partially obstructing the Outer end of the direct passage therethrough, the inlet passage having a side opening extending in a direction having a substantial component in the direction of rotation of said core, and the material of the tooth portion in which said inlet member is mounted being recessed at its leading side to provide communication between the periphery of the core and the side opening in said inlet member.

FIRST WISCONSIN TRUST COMPANY, Executor of the Estate of Robert B. Williamson,

Deceased, By H. W. GROVE,

Vice President, W. I. BARTH,

Secretary. 

